I looked at the back of the old hub to see what kind of technology the wheel sensor uses. The hub has a magnet that has a bunch of North/South magnetic poles around the circle. The wheel sensor rides just above this magnet and as the wheel turns the changes in the poles cause the sensor to send pulses to the ABS. The magnet on my old hub is very weak, would hardly pull a small screwdriver tip to it. So if a non-OEM hub has a weaker magnet, there's one possible cause. I can't get in to see how strong the magnet is on the new hub, but I did unscrew the axle nut and back the half-shaft out enough to get a piece of mechanic's wire in there to see if it attracted the wire. It did, but I couldn't make any judgement on the strength.
This really ticks me off. I did a nice job of putting this new hub in, hate to have to tear it apart again.